1. Field of the Invention
The present invention relates to a camera apparatus, or image pickup device, such for example as a video camera used in combination with a video recording apparatus such for example as a video tape recorder.
2. Description of the Prior Art
Recent years have seen widespread use of a growing number of video tape recorders in the home, and more and more video cameras are used year after year. The commercialization of home-use VTRs with integral cameras, having a weight of less than 2 kg, and lightweight handy video cameras weighing less than 1 kg, accelerates more the popularity of video cameras among people. It is expected that future video cameras will be combined with electronic cameras and will spread like still cameras available today.
Still cameras and video cameras have spread for widely different reasons. The still camera is required to produce separate still images which are beautiful and easy for people to see, while the video camera is required to make a succession of images beautiful and easy to see. Since the user of the video camera is required to have a technique to take successive images, known as "camera work", it is believed that difficulty in mastering the camera work is one of the obstacles to more widespread use of video cameras.
Now, the video camera will be analyzed from the standpoint of the level of video camera users in taking video images. In the past, video cameras have been used primarily among well-disciplined users having a high level of image taking technique, such as professional cameramen working for broadcasting stations and amateur cameramen who have acquired a high-level shooting technique. However, with the spread of video cameras among the public, video cameras are being used by more and more amateurs who have no talent and are given few opportunities to get disciplined, such as housewives and middle and aged people who have a low shooting technique level. To meet such a trend, the manufacturers have made an effort to advance a technical development for improving the ease with which video cameras are handled, other than the attempt to improve basic functions of the video camera. The final goal of such a development is to automatize the present complex camera operating procedure for allowing general people who are not skilled enough in image taking technique to produce images which approximate those taken by professional cameramen.
Various technologies for automatizing camera control processes have been developed to approach the final goal. Automatization has progressed to the point where there is automatic diaphragming, automatic focusing, and automatic white balance, and now the user can take pictures simply by depressing a picture taking button with almost no adjustment. However, almost all general users will be disappointed when they see the big difference between images taken by them with most advanced automatic video cameras and those taken by professional cameramen. This means that the final goal as described above has not yet been reached by the control process automatization. The greatest reason for the difference is that the automatization technology developed thus far for video cameras has just followed the automatization technology for still cameras, and has been effective only in making each taken image beautiful. Although successive images taken by the video cameras are required to be beautiful and easy to see, as described above, the conventional video camera manufactured with the automatization technology has only had a shoulder pad, an optimum center of gravity, and the like to meet such a requirement.
There are several reasons for the difference between successive images taken by professional and amateur cameramen. The first reason is that while the professional cameraman uses tripods when taking almost all scenes, the general video camera user takes pictures without using a tripod while carrying the camera by hand. The image taken by the layman are therefore liable to be unstable and cannot be seen well. Since the tendency is that the more video cameras spread, the smaller the ratio of tripods used, successive video images taken will become more unstable. The second reason is that images taken by home-use video cameras as they are carried by hand are more unstable than those taken by hand-held video cameras for professional use as the home-use video cameras are much lighter. Video images successively taken by the home-use video cameras get more and more unstable inasmuch as they become lighter each year. According to the third reason, the professional and amateur cameramen have different levels in the camera work. The professional cameraman has more than a few years of experience in almost all image taking modes, although the general consumers are substantially not disciplined in taking video images except for certain video camera fans. The unskilled layman has various problems in taking successive video images. They include failures in various picture taking modes, such as blurs occurring in the mode of taking still images, too fast a panning speed in the panning mode, variations in the panning speed, fluctuations of the camera in the panning mode, unstable images due to forces applied to move a zoom switch in the zooming mode, and fluctuating images taken in the dollying mode, or the mode of moving the camera with the aid of the dolly. As the video cameras become more popular among the unskilled general public, there are more users of a low image taking technique.
As described above, the requirement for technologies for producing successive images easy to see will be increased, rather than reduced, and will be of great importance.
Semiconductor technology has made much progress in the industry. CCD imaging panels of the size 4.4 mm.times.5.7 mm have now been fabricated on a trial basis. Efforts have been made at a high rate toward a higher-packing density and a lower cost. It is expected that successive video images will be corrected solely electronically by using an imaging panel having abundant pixels and controlling the process of reading the pixels. Therefore, an important technical aim to achieve in the industry will be the development of a handy home-use video camera which allows a novice to take successive video images as stable as those taken by the hand-held video camera manipulated by a professional cameraman in various picture taking modes such as dollying, panning, tilting, and zooming, even without using a tripod.
The prior art directed to accomplish the foregoing aim will be reviewed. At least at present, there is no video camera realized as a product or commercialized which has functions to meet the above-mentioned requirement.
Video cameras used in combination with conventional video tape recorders comprise in combination a focusing means such as a lens and an image pickup means such as a CCD imager, which are fixed with accuracy and assembled together. Those video cameras are ineffective in suppressing ordinary image fluctuations caused by hand-induced blurs when a telephoto lens is used, and also ineffective in suppressing image fluctuations due to unsmooth camera rotation when the video camera is rotated at varying speed in the panning mode.
The prior art which appears most likely to achieve a video camera of simple construction and low cost is disclosed in Japanese Laid-Open Utility Model Publication No. 53-8938 for "Optical axis stabilizer device". The claimed invention is concerned with an optical axis stabilizer device comprising an even number of reflecting mirrors disposed in confronting relation on an optical path for successively reflecting an incident ray of light, at least one inertial load disposed on the optical axis and supported for angular movement, and means for reducing the angle of angular movement of the inertial load to 1/2 and transmitting the reduced angle to any of the reflecting mirrors. The disclosed arrangement aims to suppress image fluctuations through the inertial load which is low in cost and simple in construction.
However, the above prior-art arrangement has suffered the following problems:
The first problem is that since the image fluctuations are suppressed only by the inertial load, errors will be accumulated and reach the limit of a suppressing range in a short time when the image fluctuations continue for some time, with the result that the device will not function sufficiently as a product. Therefore, the prior invention has little advantage when carried out. For cancelling the image fluctuations, there should be an optimum ratio between the moment of inertia of the rotational shaft of each reflecting mirror and the moment of inertia of the inertial load, and if such an optimum ratio were not met, the device would not work. However, the disclosed invention is silent as to the optimumm ratio, and hence is merely an invention showing an idea only and would not work well if reduced to practice.
The second problem is as follows: If the optimum ratio were found and the device worked, the device would be effective to somewhat suppress image fluctuations in the telephoto mode in which images are taken only in one direction, and would be effectively used in a still camera mode of taking images at a fixed point. However, when used in taking images in varying directions as a video camera, the image-taking direction would not be changed if the direction of the camera body were changed at the time of carrying the camera by hand. When the direction of the camera body is changed, the limit of the fluctuation suppressing range would be reached, and then the image would start to move. At this time, not only the image would be disturbed largely, but also the device would no longer be effective in suppressing image fluctuations thereafter. In addition, the direction of the camera body and the picture-taking direction would differ from each other, so that the device would be highly difficult to handle. Furthermore, since the prior device fails to stabilize images in modes other than the fixed-frame picture-taking mode, the device has merit in being carried out for use as a video camera though it is of a low cost.
Some apparatus for preventing image fluctuation for optical apparatus are disclosed in U.S. Pat. Nos. 3,212,420, 3,378,326, and 3,473,861, but these are not suitable for video cameras. Japanese Published Patent No. 56-21133 discloses an apparatus for preventing image fluctuation usable for a video camera, but it is too heavy in weight and too poor in performance to be used as a practical video camera.
The industry has not been interested in developing video cameras with the foregoing functions for the reason that in normal picture-taking or imaging modes in broadcasting stations, it is customary to use tripods if possible, and successive video images thus taken are sufficiently beautiful and easy to see even without taking special precautionary measures. When taking images without using the tripod such as for news materials, the sophisticated technique or camera work of a professional cameraman is used to produce successive images of a desired image quality. Accordingly, no strong demand has existed in the art for image stabilizer devices. Although there are needs for such devices in fields requiring strict imaging conditions, the required characteristics are quite stringent. As the need for video cameras having an image stabilizing capability under normal imaging conditions does not originate from broadcasting stations, the industry has had no concern for such video cameras, and substantially no prior art has been developed for the technology for stabilizing video images taken under normal conditions.
The home-use video camera industry has directed attention to improving the quality of still video images, and will direct attention to improving the quality of successive video images in a few years after the present trend of development will have come to an end. Stated otherwise, no prior art has been developed for achieving low-cost video cameras, for either home use or industrial use, having an automatic ability to improve the quality of successive images which would be unstable and not easy to see that are taken by general consumers under normal hand-held conditions.